The present invention relates generally to the field of wireless communications, and particularly to the design of multi-band antennas.
Certain applications such as the Global System for Mobile Communications (GSM) and Personal Communications Service (PCS) require that multiple bands be accessible, depending upon the local frequency coverage available from a service provider. In order to utilize a specific band for a specific application (i.e., in the context of a multi-band-capable antenna), an adjunct piece of hardware like a duplexer or filter can be used. The subject of the present invention, however, obviates the need for an adjunct duplexer or filter through an integrated filter. These filters can be either in-line or attached directly to the antenna element.
Because applications such as GSM and PCS are used in the context of wireless communication devices that have relatively small form-factors, a low profile is also a required feature of these antennas.
The present invention addresses the requirements of certain wireless communications applications by providing a configuration for multi-band, low-profile, capacitively loaded antennas with integrated filters.
This invention allows for multiple antenna elements in myriad physical configurations to cover one to n number of frequencies or bands of frequencies.
In all embodiments of the present invention there are antenna elements with both inductive and capacitive parts. Each antenna element, regardless of variations in physical design of the element, provides a single frequency or band of frequencies.
In one embodiment a single antenna element has one unshaped top plate and one bottom plate. In all embodiments, each antenna element produces a specific frequency or band of frequencies based on its relative size and shape. Different physical configurations can also be considered to adapt the antenna and its elements to the physical environment specific to a particular application.
Once the antenna elements have been cut and folded into the desired form for the purpose of matching a frequency or frequency band, they can then be arranged to target multiple bands. In one embodiment, the antenna elements can be placed one next to the other. In another embodiment, the antenna elements can be stacked, one on top of another. In yet another embodiment, the elements can be inserted one inside the other.
In all embodiments, integrated filters are used to reject unused bands. In one embodiment, the filter is a formed piece of metal that is attached to the underside of one arm of the antenna element. In another embodiment, the filter is cut out of one arm of the antenna element. Whatever the single embodiment of the filter, all of the various embodiments can be combined in a variety of physical configurations to meet the requirements of a given application. Once the multiple antenna elements have been cut, folded, and arranged to both meet the frequency and space requirements of the specific application, one has a multi-band, low-profile, capacitively loaded antenna with integrated filters.
This summary does not purport to define the invention. The invention is defined by the claims.